An apparatus of this type known from EP-B-0 206 186 has a top transverse transporting tube and a bottom transverse transporting tube which are driven in time with the forming machine, are guided, in the forming region of the machine, in stationary bearings so as to be able to move back and forth, and on which there are respectively fitted a top tong casing and a bottom tong casing. In order to form a unit which can be displaced with sliding action, the two transverse transporting tubes are connected by a yoke. Workpieces are seized by means of pairs of interacting tong grippers, one being arranged in the top tong casing, and the other being arranged in the bottom tong casing, and the opening and closing movements of the tongs, formed by the respectively interacting tong grippers, being controlled, via transmission levers, by control shafts, arranged rotatably in the transverse transporting tubes, in the form of camshafts. The operation, necessary in hot-forming machines, of seizing workpieces of very different sizes is easily made possible by tongs of this type.
A disadvantage of this apparatus is that, in order to seize a workpiece, a tong gripper has to be advanced up to the workpiece from beneath, as a result of which there is considerable danger of the tong gripper colliding with falling parts. Moreover, in particular in hot-forming machines, the tong grippers are exposed to pronounced soiling, for example by lubricants and/or scale and/or water. In addition, two camshafts are necessary for controlling the opening and closing movements of the tongs and two transverse transporting tubes are necessary for moving the tongs back and forth, and this means that the movements of the two camshafts and of the two transverse transporting tubes have to be coordinated in each case.